Microlithographic projection exposure apparatus and measuring device for a projection lens

ABSTRACT

A microlithographic projection exposure apparatus includes a projection lens that is configured for immersion operation. For this purpose an immersion liquid is introduced into an immersion space that is located between a last lens of the projection lens on the image side and a photosensitive layer to be exposed. To reduce fluctuations of refractive index resulting from temperature gradients occurring within the immersion liquid, the projection exposure apparatus includes heat transfer elements that heat or cool partial volumes of the immersion liquid so as to achieve an at least substantially homogenous or at least substantially rotationally symmetric temperature distribution within the immersion liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of International Patent ApplicationPCT/EP2005/000246, which was filed on Jan. 13, 2005 and claims benefitof U.S. provisional application Ser. No. 60/537,784 filed Jan. 20, 2004.The full disclosure of these earlier applications is incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to microlithographic projection exposureapparatuses as used for manufacturing highly-integrated electricalcircuits and other microstructured components. In particular, theinvention relates to projection exposure apparatuses configured forimmersion operation. The invention further provides measuring devicesfor determining the imaging properties of projection lenses.

2. Description of Related Art

Integrated electrical circuits and other microstructured components areusually manufactured by applying a plurality of structured layers to asuitable substrate, which may be, for example, a silicon wafer. Tostructure the layers, they are first covered with a photoresist that issensitive to light of a given wavelength range, e.g. light in the deepultraviolet (DUV) spectral range. The coated wafer is then exposed in aprojection exposure apparatus. A pattern composed of structures locatedon a mask is imaged on the photoresist by means of a projection lens.Because the imaging scale is generally less than 1:1, such projectionlenses are frequently referred to as reduction lenses.

After the photoresist has been developed the wafer is subjected to anetching or deposition process whereby the uppermost layer is structuredaccording to the pattern on the mask. The remaining photoresist is thenremoved from the remaining parts of the layer. This process is repeateduntil all the layers have been applied to the wafer.

One of the primary design objectives in the development of projectionexposure apparatuses is to be able to lithographically define structuresof increasingly small dimensions. Small structures lead to highintegration densities, which generally have a favourable effect on theefficiency of microstructured components manufactured using suchapparatuses.

The size of the definable structures depends, above all, on theresolution of the projection lens used. Because the resolution ofprojection lenses improves as the wavelength of the projection lightbecomes shorter, one approach to decrease the resolution is to useprojection light having shorter and shorter wavelengths. The shortestwavelengths currently used are 193 nm and 157 nm, i.e. in the deepultraviolet (DUV) spectral range.

Another approach to decrease the resolution is based on the concept ofintroducing an immersion liquid having a high refractive index into thespace located between a last lens of the projection lens on the imageside and the photoresist or another photosensitive layer to be exposed.Projection lenses, which are designed for immersion operation and aretherefore also referred to as immersion lenses, can attain numericalapertures of greater than 1, e.g. 1.3 or 1.4. However, immersion notonly makes possible high numerical apertures and therefore an improvedresolution, but also has a favorable effect on depth of focus. Thegreater the depth of focus, the less high are the demands for precisepositioning of the wafer in the image plane of the projection lens.

A projection exposure apparatus designed for immersion operation isknown from U.S. Pat. No. 4,346,164 A. To accommodate a wafer, this knownprojection exposure apparatus has an upwardly open container with anupper edge that is located higher than the lower boundary face of thelast lens of the projection lens on the image side. Inlet and outletpipes for an immersion liquid open into the container. These pipes areconnected to a pump, a temperature-stabilizing device and a filter forcleaning the immersion liquid. During operation of the projectionexposure apparatus, the immersion liquid is circulated in a loop. Animmersion space located between the lower boundary face of the last lensof the projection lens on the image side and the semiconductor slice tobe exposed remains filled the immersion liquid.

A projection exposure apparatus having an immersion arrangement is alsoknown from WO 99/49504. In this projection exposure apparatus the supplyand discharge pipes for the immersion liquid open directly onto thelower boundary face of the last lens of the projection lens on the imageside. The use, in particular, of a plurality of such supply anddischarge pipes, which may be arranged, for example, in a ring aroundthe last lens on the image side, makes it possible to dispense with asurrounding container. This is because immersion liquid is sucked awayas it runs off laterally and is fed back in such a way that theimmersion space between the last lens on the image side and thephotosensitive surface always remains filled with immersion liquid.

A difficulty with the immersion operation of projection exposureapparatuses is to keep the optical characteristics of the immersionliquid constant, at least where the liquid is exposed to the projectionlight. Special attention must be paid to the absorption and therefractive index of the immersion liquid. Local fluctuations in theabsorption, as can be produced, for example, by impurities, lead toundesired intensity fluctuations in the image plane. As a result, linewidth fluctuations may occur even if the imaging is otherwise free ofsubstantial aberrations.

Local fluctuations in the refractive index of the immersion liquid havean especially detrimental effect, since such fluctuations directlyimpair the imaging characteristics of the projection exposure apparatus.If the refractive index of the immersion liquid is inhomogeneous withinthe volume of the immersion liquid exposed to the projection light, thiscauses distortions of the wave fronts passing through the immersionspace. For example, points in the object plane of the projection lensmay no longer be imaged sharply on the image plane.

The refractive index of liquids is dependent on their density. Becauseliquids are virtually incompressible, their density is practicallyindependent of static pressure and depends almost exclusively on thetemperature of the liquids. For this reason, the immersion liquid insidethe immersion space that is exposed to the projection light can have ahomogeneous refractive index only if the temperature of the immersionliquid is constant therein. Moreover, temperature fluctuations withinthe immersion liquid not only cause fluctuations of refractive index,but can also cause adjacent optical elements, in particular the lastoptical element of the projection lens on the image side, to be heatedunevenly and therefore to be deformed in a manner that can hardly becorrected.

The causes that give rise to inhomogeneities of the temperature in theimmersion space are diverse. A major cause for heating the immersionliquid is the absorption of projection light by the immersion liquid.Even if only a small percentage of the projection light is absorbed bythe immersion liquid, this causes a comparatively high heat inputbecause of the short-wave and therefore energy-rich projection light. Aneffect which leads to cooling of the immersion liquid is the evaporationof immersion liquid at the boundary surface to a surrounding gas. Inaddition, the temperature of the immersion liquid is influenced by heattransitions from and to surrounding solid bodies. These bodies may be,for example, a heated last lens of the projection lens, its housing orthe wafer to be exposed.

To homogenize the temperature, it has been proposed hitherto tocirculate the immersion liquid in a circuit and to establish a desiredreference temperature by means of a temperature-stabilizing device.However, the homogenization of temperature distribution that can beachieved in this way is frequently not sufficient. Relatively high flowvelocities, which may lead to disturbing vibrations, are usuallyrequired. In addition, high flow velocities promote the formation of gasbubbles which can also adversely affect the imaging properties.

Moreover, similar difficulties also arise in measuring devices withwhich the imaging characteristics of such projection lenses can bedetermined. If immersion lenses having numerical apertures of greaterthan 1 are to be measured, it is also necessary to introduce animmersion liquid into an immersion space located between the lastoptical element of the projection lens on the image side and a testoptics component of the measuring device. Because of the extremely highdemands on the measuring accuracy of such devices, inhomogeneities ofrefractive index within the immersion liquid cannot be tolerated.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to improve a projectionexposure apparatus, and a measuring device for the optical measurementof projection lenses, such that imaging defects resulting frominhomogeneities of the refractive index within the immersion liquid arereduced.

This object is achieved in that the projection exposure apparatus andthe measuring device include a heat transfer element with which thetemperature can be changed in a specified manner in a partial volume ofthe immersion space.

The invention is based on the discovery that a desired temperaturedistribution within the immersion space can be attained if heat issupplied to or extracted from the immersion liquid in a spatiallyspecified manner. It is known in general where and to what degree heatis transferred into the immersion liquid or dissipated therefrom tosurrounding media. If these causes of temperature fluctuations arecarefully analyzed, it is possible to determine the temperaturedistribution which the immersion liquid inside the volume of theimmersion space through which projection light passes can be expected tohave, if no additional measures are taken to change the temperaturedistribution. On the basis of the anticipated temperature distributionit can then be determined at which locations heat must be supplied orextracted so that the desired temperature distribution is established.In general, the aim is to achieve a homogenous temperature distribution.However, consideration may also be given to establishing a temperaturedistribution which, although inhomogeneous, has a certain symmetry. Forexample, with a rotationally symmetrical temperature distribution theimmersion liquid would not be free from refractive power but could havethe effect of an index lens.

Because of the local heating or cooling of the immersion liquidaccording to the invention, continuous circulation of the immersionliquid in a circuit including a temperature-stabilizing arrangement maybe dispensed with, if desired. In this way vibrations produced by thecirculation of the immersion liquid are avoided, as is particularlyadvantageous in the case of measuring devices. If the immersion liquidis not to be completely exchanged at regular intervals, considerationmay be given to a discontinuous circulation. This means that theimmersion liquid is circulated by means of a pump, while being cleanedand optionally additionally cooled or heated, only during exposure ormeasuring pauses. With regard to the avoidance of vibration, suchdiscontinuous circulation may be advantageously used even independentlyof the heat transfer element according to the invention.

If a homogeneous temperature distribution is desired, this willgenerally result in the heat transfer elements being arranged with asymmetry corresponding to that of the immersion space. Rotationallysymmetrical arrangements of the heat transfer elements are thereforepreferred. In the case of slit-shaped light fields, as are projectedonto the wafer with projection exposure apparatuses designed forscanning operation, for example, the heat transfer elements may also bearranged differently, e.g. corresponding to the geometry of the lightfields.

As a heat transfer element, any body that is suited to exchanging heatwith the immersion liquid by way of thermal conduction or radiation isin principle possible. Depending on whether heat passes from the heattransfer element to the immersion liquid or vice versa, local heating orcooling of the immersion liquid occurs.

The heat transfer element may be arranged, for example, inside theimmersion space, so that it comes into contact with the immersion liquidduring immersion operation. In the simplest case, the heat transferelement is then an electrically heatable heating wire which ispreferably covered with an electrically insulating and chemicallyprotective layer. Such a heating wire has the advantage that it can begiven practically any desired shape. As a result, heat can be suppliedto the immersion liquid at any desired location inside the immersionspace but outside the volume through which the projection light passes.

Because the projection light generally produces a relatively large heatinput due to absorption, the heating wire may be arranged, for example,in an annular configuration around the volume through which projectionlight passes. The calorific output is then preferably selected such thatthe temperature gradient in the volume through which projection lightpasses is minimized.

A still more precisely specified heat input is possible if, as anadditional parameter, the wire diameter is varied. In this way thecalorific output can also be varied along the longitudinal extension ofthe heating wire.

Instead of an electrically heatable heating wire, a conduit throughwhich a fluid heating medium flows, e.g. heated or cooled water, mayalso be used as a heat transfer element.

In this case, too, the heating or cooling power can be varied in thelongitudinal direction of the conduit by varying the flow cross-section.

If the immersion liquid is prevented from escaping by a wall laterallybordering the immersion space, the heat transfer element may also bearranged in this wall. Also in this case a configuration of the heattransfer element as an electrically heatable heating wire or a conduitthrough which a heating medium can flow is contemplated. In this way thewall itself forms, so to speak, a single large heat transfer element.

For locally cooling the immersion liquid a Peltier element may be usedas heat transfer element.

In an particularly advantageous embodiment, the heat transfer element isspaced from the immersion space in such a way that heat can be exchangedbetween the heat transfer element and the partial volume by thermalradiation, e.g. by infrared or microwave radiation. In this case theheat transfer element may be, for example, in the form of a preferablyelectrically heatable or coolable planar radiator. Heat transfer byradiation has the advantage over heat transfer by conduction that nodirect physical contact between the heat transfer element and theimmersion liquid is required. The heat transfer element can therefore bearranged at a greater distance from the immersion liquid. In thisembodiment, possible difficulties arising through the installation ofheat transfer elements in the narrow immersion space or adjacentlythereto are avoided.

In order to direct the thermal radiation more selectively from a heattransfer element to the immersion liquid in this embodiment, one or moreoptical elements, for example mirrors or lenses, which change thedirection of the thermal radiation may be arranged between the heattransfer element and the immersion space. By using optical elementshaving positive refractive power, thermal radiation can be focused in aspecified manner into the narrow gap between the projection lens and thewafer and onto the desired partial volume of the immersion space.

In principle, it is even possible to arrange one or more of theseoptical elements inside the projection lens in order to direct thermalradiation onto the desired partial volume of the immersion space. It isalso possible in this case to couple thermal radiation into the beampath of the projection lens in such a way that said thermal radiationexits the last lens of the projection lens on the image side separatelyfrom the projection light. With a suitably selected beam path, thethermal radiation heats exclusively a partial volume of the immersionliquid which surrounds the volume through which the projection lightpasses, thus reducing the temperature gradient at the edge of thisvolume. It must then be ensured only that the thermal radiation has awavelength to which the photoresist is insensitive.

To measure the temperature in the immersion liquid in a contactlessmanner, the temperature of a heat transfer element may be determined,wherein the temperature of the heat transfer element can be changed onlyby exchange of thermal radiation with the immersion liquid. Under theseconditions, given a known calorific output and temperature of the heattransfer element, conclusions may be drawn regarding the temperature ofthe immersion liquid. To measure the temperature of such a heat transferelement, it may be connected to a thermal sensor. The latter may in turnbe in signalling connection to a control device which regulates theheating or cooling output of the heat transfer element.

In the case of projection exposure apparatuses which are not operated inscanning mode but step-by-step, a wafer stage, on which the carrier ofthe photosensitive layer can be fixed, may be considered as a locationfor mounting a heat transfer element according to the invention. In thisway the carrier may be locally heated or cooled from below. Thus, thetemperature of the immersion liquid located above the carrier can alsobe changed by thermal conduction. This configuration also provides apossibility of cooling the volume of immersion liquid exposed to theprojection light. Other cooling measures are in general difficultbecause this volume is not easily accessible either from above or fromthe side.

According to another aspect of the invention, the above-mentioned objectis achieved in that an evaporation barrier, which at least partiallysurrounds the immersion space, is arranged on an underside of theprojection lens facing towards the photosensitive layer.

According to this second aspect of the invention, one of the majorcauses leading to the formation of temperature gradients in theimmersion space is largely eliminated. The evaporation barrier preventsimmersion liquid from evaporating to a large extent into a surroundinggas volume.

For this purpose the evaporation barrier may include, for example, oneor more at least approximately concentric rings having, for example, acircular or polygonal shape, which are arranged at a distance from oneanother. In this way the boundary surface to the surrounding gas isreduced so that less immersion liquid can evaporate.

According to a further aspect of the invention the evaporation ofimmersion liquid is wholly or at least partially prevented in that anouter chamber surrounding the immersion space and in fluid connectiontherewith can be enriched with a vapor phase of the immersion liquid.

Through the enrichment of this outer chamber with a vapor phase of theimmersion liquid the vapor pressure in the outer chamber can beincreased until hardly any immersion liquid can pass from the liquidphase to the vapor phase. In the ideal case, the pressure of the vaporphase in the outer chamber is adjusted such that it at leastapproximately equals the saturation vapor pressure of the vapor phase atthe temperature prevailing in the outer chamber. In this case, exactlythe same amount of immersion liquid evaporates at the boundary surfacebetween the immersion liquid and the vapor phase as simultaneouslycondenses from the vapor phase. As a result of this equilibrium, thetemperature of the immersion liquid in proximity to the boundary surfaceremains unchanged.

To producing a vapor phase of the immersion liquid in the outer chamber,a supply device for introducing a vapor phase of the immersion liquidinto the outer chamber may be provided.

The embodiments explained below can be advantageously used with all theabove aspects of the invention and even independently thereof.

The feed pipes for the immersion liquid are normally firmly connected,e.g. clamped or press-fitted, to a wall delimiting the immersion spacelaterally and downwardly. This may transfer vibrations from outside tothe immersion liquid. To avoid such vibrations, in particular withmeasuring devices, an aperture for a pipe leading into the immersionspace may be provided in such a wall. The dimensions of the aperture aresufficiently larger than the external dimensions of the pipe so thatimmersion liquid can enter a gap remaining between the pipe and thewall, but cannot flow out of said gap as a result of adhesion forces.The adhesion forces therefore effect a seal of the wall in the region ofthe aperture although the pipe is longitudinally displaceable therein. Atransmission of vibrations from the pipe to the wall and from there tothe immersion liquid is considerably reduced by the liquid-filled gap.

In addition, it is advantageous if a detector for detecting immersionliquid is provided. In particular with projection exposure apparatusesor measuring devices in which the immersion liquid is not delimitedlaterally by a ring or a container, it is frequently necessary toascertain whether immersion liquid is still present inside the regionprovided therefore or has left this region, e.g. as a result of inertialforces.

It may be possible to determine, with the help of the detector, whetherimmersion liquid leaves a predefined closed surface. This closed surfaceis preferably a surface on the photosensitive layer immediately belowthe projection lens.

Such a detector may be realized, for example, in that two substantiallyparallel conductors, preferably placed around the closed surface in themanner of the loop, form a capacitor. If immersion liquid enters thespace between the conductors, this causes an increase in the dielectricconstant, whereby the capacitance of the capacitor is increased. Thisincrease in capacitance can be detected in a simple manner with asuitable measuring circuit, known per se, for measuring capacitance.

The embodiments of the invention explained above have been explainedpredominantly with reference to a projection exposure apparatus.However, they can be used equally advantageously with measuring devicesfor determining imaging characteristics, since a measuring assembly formeasuring a projection lens differs only slightly from a projectionexposure apparatus. For example, measuring devices also include a typeof illumination system which generates measuring light and couples itinto the projection lens. If no photosensitive test layer is exposedduring measurement, the immersion space is delimited downwardly by atest optics component. With a Twyman-Green or Fizeau interferometer, forexample, this test optics component may be a mirror; with a Moiré orShearing interferometer it may be a diffraction grating, and with aHartmann-Shack sensor it may be a grid-of-points mask.

If an immersion liquid is introduced into the gap between the lastoptical element of the projection lens on the image side and such a testoptics component, temperature stabilization of this immersion liquid isalso required. Because the test optics component—unlike the wafer in aprojection exposure apparatus designed for scanning operation—generallydoes not move within the image plane, the immersion liquid in theimmersion space is not mixed as a result of such movements, so thatstill higher temperature gradients can develop. On the other hand, someof the above-mentioned measures are especially suited to such measuringdevices, since design difficulties arising as a result of scanningmotion do not occur in their case.

Such a stationary test optics component delimiting the immersion spacedownwardly enables heat to be dissipated in a specified manner via thetest optics component. If, for example, the test optics componentincludes a zone which is at least partially transparent to light and ifthis zone is at least partially surrounded by another zone, this otherzone may be made of a material which has higher thermal conductivitythan the material of which the light-transparent zone consists. Anexample is a glass/metal material combination. The metal surrounding theglass zone ensures efficient heat dissipation for the immersion liquidlocated above same.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the present invention may be morereadily understood with reference to the following detailed descriptiontaken in conjunction with the accompanying drawing in which:

FIG. 1 shows a meridional section through a projection exposureapparatus according to the invention in a greatly simplifiedrepresentation which is not to scale;

FIG. 2 shows an enlarged portion of the projection exposure apparatusillustrated in FIG. 1, in which a heat transfer element in the form of aheatable ring recessed in a housing of the projection lens on the imageside can be seen;

FIG. 3 is a perspective representation of an immersion space accordingto another embodiment of the invention in which the heat transferelement is a heating wire arranged inside the immersion space;

FIG. 4 shows an axial section through the immersion space illustrated inFIG. 3;

FIG. 5 is a representation corresponding to FIG. 3 according to afurther embodiment of the invention in which the heat transfer elementis integrated in a wall laterally delimiting the immersion space;

FIG. 6 is a representation corresponding to FIG. 4 according to afurther embodiment of the invention in which the heat transfer elementsare thermal radiators;

FIG. 7 is a representation corresponding to FIG. 4 according to yetanother embodiment of the invention in which heat transfer elements arerecessed in a wafer stage for fixing a wafer;

FIG. 8 is a representation corresponding to FIG. 4 according to anotheraspect of the invention in which an evaporation barrier surrounds theimmersion space laterally to reduce evaporation;

FIG. 9 shows a partial meridional section through a projection exposureapparatus according to a further aspect of the invention in which asaturated vapor phase of the immersion liquid is located above theimmersion liquid to reduce evaporation;

FIG. 10 shows a portion of the projection exposure apparatus illustratedin FIG. 9 in which a floating fixing of an inlet pipe is shown;

FIG. 11 is a representation based on FIG. 9 of a projection exposureapparatus according to yet a further aspect of the invention in whichthe immersion liquid is circulated through the influence of gravity;

FIG. 12 is a representation corresponding to FIG. 3 of a furtherembodiment of the invention in which a detector for detecting laterallyescaping immersion liquid is provided;

FIG. 13 shows an axial section through the immersion space illustratedin FIG. 12;

FIG. 14 shows an axial section through an immersion space of a pointdiffraction interferometer according to a first embodiment, and

FIG. 15 shows an axial section corresponding to FIG. 14 according to asecond embodiment of a point diffraction interferometer according to theinvention;

FIG. 16 shows in a partial perspective representation a projectionexposure apparatus according to still another embodiment if theinvention in which a plurality of inlets and outlets are provided in thevicinity of the immersion space;

FIG. 17 a cross section through an inlet shown in FIG. 16;

FIG. 18 is a representation similar to FIG. 7 according to yet anotherembodiment of the invention in which a temperature sensor is received ina wafer stage.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a meridional section through a microlithographic projectionexposure apparatus designated as a whole by 10 in a greatly simplifiedrepresentation. The projection exposure apparatus 10 includes anillumination system 12 for generating projection light 13, whichcomprises a light source 14, illumination optics indicated at 16 and anaperture 18. In the embodiment illustrated the projection light 13 has awavelength λ of 193 nm. The projection exposure apparatus 10 alsoincludes a projection lens 20 containing a multiplicity of lenses, onlysome of which are indicated as examples in FIG. 1 for reasons ofclarity, and which are denoted by L1 to L5. The projection lens 20serves to image a mask 24 arranged in an object plane 22 of theprojection lens 20 on a reduced scale on a photosensitive layer 26. Thelayer 26, which may consist, for example, of a photoresist, is arrangedin an image plane 28 of the projection lens 20 and is applied to acarrier 30.

The carrier 30 is fixed to the bottom of a basin-like, upwardly opencontainer 32 which is movable parallel to the image plane 28 (in amanner not illustrated in detail) by means of a traversing device. Thecontainer 32 is filled with an immersion liquid 34 to a level at whichthe last lens L5 of the projection lens 20 on the image side is immersedin the immersion liquid 34 during operation of the projection exposureapparatus 10. Instead of a lens, the last optical element of theprojection lens 20 on the image side may be, for example, aplane-parallel terminal plate. The refractive index of the immersionliquid 34 approximately coincides with the refractive index of thephotosensitive layer 26. In the case of projection light having awavelength of 193 nm or 248 nm, high-purity deionized water, forexample, is possible as the immersion liquid 34. With shorterwavelengths, such as 157 nm, perfluoropolyether (PEPE), for example,which is commercially available under trade names including Demnum® andFomblin®, is suitable.

The container 32 is connected via an inlet pipe 36 and an outlet pipe 38to a conditioning unit 40 in which elements including a circulation pumpand a filter for cleaning the immersion liquid 34 are contained. Theconditioning unit 40, the inlet pipe 36, the outlet pipe 38 and thecontainer 32 together form an immersion device designated 42 in whichthe immersion liquid 34 circulates while being cleaned and maintained ata constant temperature. The absolute temperature of the immersion liquid34 should be set as accurately as possible since imaging by theprojection lens 20 can be impaired by focusing errors and image shelldefects in the case of deviations from the reference temperature. Suchimaging defects may in turn lead to a reduction in size of the processwindow available for an exposure.

FIG. 2 shows an enlarged portion of the projection exposure apparatusshown in FIG. 1 in which further details can be seen. In FIG. 2 a gap,referred to hereinafter as the immersion space, which remains betweenthe last lens L5 of the projection lens 20 on the image side and thephotosensitive layer 26, is designated 44. For reasons of clarity theheight h of the immersion space 44, i.e. the axial distance between thelast optical element of the projection lens 20 on the image side and thephotosensitive layer 26, is greatly exaggerated as represented in FIG. 2and in the other Figures; in fact, the height h is of the order ofmagnitude of only one or a few millimeters. In the embodimentillustrated, the immersion space 44 is completely filled with immersionliquid 34, which flows past the projection lens 20 in a circulationdirection indicated by 46.

The projection light indicated by 13 enters the immersion liquid 34 viathe last lens L5 on the image side and passes through said immersionliquid 34 in the zone of a partial volume 48 shaded grey in FIG. 2. Theshape of the volume 48 depends on the numerical aperture NA of theprojection lens 20 and on the geometry of the light field that isprojected by the projection lens 20 onto the photosensitive layer 26.Because the immersion liquid 34 has an absorption—although a smallone—for the projection light 13 of the given wavelength, a part of theprojection light 13 is absorbed within the volume 48. The heat releasedin this way flows into the partial volume of the immersion space 44surrounding the partial volume 48, since the temperature is lowertherein, unless suitable countermeasures are taken.

The heat dissipated outwardly leads to the formation of a temperaturegradient also within the volume 48. Because the refractive index of theimmersion liquid 34 is temperature-dependent, this temperature gradientwithin the volume 48 causes a corresponding gradient in the refractiveindex. Such a gradient causes a refractive power which manifests inimaging defects that, if they exceed a certain degree, cannot betolerated. This effect occurs especially strongly if the immersionliquid 34 in the immersion space 44 does not move or moves only slowly,since the heat produced by absorption in the volume 48 is not, or isonly slightly, carried away by convection. For this reason immersiondevices in which the immersion liquid does not circulate, or does notcirculate permanently, with a high flow velocity are especially affectedby these heat-induced effects.

In addition, the boundary surfaces between the immersion liquid 34 and asurrounding gas or gas mixture, which may be e.g. air or an inert gassuch as helium or nitrogen, also contribute to the formation of atemperature gradient. At these boundary surfaces, which are designated47 in FIGS. 1 and 2, the immersion liquid 34 evaporates which consumesvaporization heat. In this way the immersion liquid 34 is continuouslycooled at the boundary surfaces 49, while the volume 48 is heated by theprojection light 13.

In order to reduce or even completely avoid the imaging defectsaccompanying a temperature gradient a heat transfer element is provided.In the embodiment of FIGS. 1 and 2, this heat transfer element isrealized as a heatable ring 50 that is recessed in the underside 49 ofthe projection lens 20 which is immersed in the immersion liquid 34. Theheat emitted from the ring 50 is transmitted by thermal conduction tothe immersion liquid 34, as is indicated by arrows 52 in FIG. 2. In thisway the partial volume of the immersion space 44 surrounding the partialvolume 48 is additionally heated, counteracting the formation of atemperature gradient. The geometry of the ring 50 may be adapted to theshape of the volume 48. In the case of a rectangular light field, forexample, the heat transfer element 50 may also be configured as arectangular ring. It is, of course, also possible to replace thecontinuous ring by a plurality of individual heat transfer elementsdistributed with corresponding geometry on the underside 49 of theprojection lens 20.

FIGS. 3 and 4 show a projection exposure apparatus according to anotherembodiment in a partial perspective representation and in axial sectionrespectively. In this embodiment the immersion liquid 34 is not locatedin a container 32 but is retained in the immersion space 44 solely byadhesion forces. In the illustrated embodiment the last optical elementof the projection lens 20 on the image side is not a lens but aplane-parallel terminal plate 54. Indicated thereon is a projectionlight beam denoted by 56 which has an approximately rectangularcross-section. After passing through the terminal plate 54 and theimmersion liquid 34 located in the immersion space 44 below saidterminal plate 54, the projection light beam 56 generates a rectangularlight field 58 on the photosensitive layer 26.

In this embodiment the temperature gradient is even steeper than thatshown in FIGS. 1 and 2, since the boundary surface 47 between theimmersion liquid 34 and a surrounding gas, which boundary surface 47 iscomparatively cool as a result of evaporation, is here located evencloser to the volume 48. In addition, in this embodiment the immersionliquid 34 is not circulated, but remains for a prolonged period in theimmersion space 44. In this case, a certain homogenization of thetemperature distribution is provided only by mixing of the immersionliquid 34 as a result of a traversing motion 60, indicated by an arrow60, by which the photosensitive layer 26 is moved past the projectionlens 20 during an exposure.

To counteract the formation of a major temperature gradient, in theembodiment illustrated in FIGS. 3 and 4 heat is supplied to theimmersion liquid 34 via an annular heating wire 501 that is surroundedby a chemically inert and electrically insulating sheath. The heatingwire 501 is connected to a control unit 62 in which a battery forcurrent supply and a control device are integrated. Said control unit 62has the function of adjusting the calorific output of the heating wire501 in accordance with a predefined value. Instead of the controldevice, a temperature control system which includes a temperature sensorfor measuring the temperature of the immersion liquid 34 may beprovided.

In the embodiment illustrated, the heating wire 501 is in the form of aloop placed around the volume 48 through which the projection light beam56 passes, so that the immersion liquid 34 located outside the volume 48can be uniformly heated by the heating wire 501. The heating wire 501may also be arranged more tightly around the volume 48. Moreover, shapesof the heating wire 501 other than circular are, of course, envisaged inthe context of the present application.

FIG. 5 shows a further embodiment based on the representation in FIG. 3,indicating how heat transfer elements may be configured to reduce thetemperature gradient. In this embodiment the immersion space 44 isdelimited laterally by a ring 62 fixed to the underside 49 of theprojection lens 20. The ring 62 extends downwardly in the axialdirection only so far that the photosensitive layer 26 can be moved pastand below the ring 62 during a traversing movement 60. The ring 62 hasthe effect that, with relatively fast traversing movements 60, theimmersion liquid 34 does not escape from the immersion space 44. Inaddition, the boundary surface 47 to the surrounding gas or gas mixtureis considerably reduced, since the immersion liquid 34 can now evaporateonly via a narrow gap of height d remaining below the ring 62.

To homogenize the temperature distribution, the ring 62 is heatable. Forthis purpose an annular conduit 502, in which a heating medium, e.g.heated water or hot air, can circulate is arranged in the lower part ofthe ring 62.

FIG. 6 shows in a partial axial sectional representation a projectionexposure apparatus according to a further embodiment. In this case theheat transfer elements are realized as planar radiators 503 which areelectrically heatable and are distributed around the perimeter of theprojection lens 20. The planar radiators 503 have a black surface ontheir side facing towards the immersion liquid 34 and a mirror surfaceon the opposite side, so that thermal radiation is directedsubstantially only at the immersion liquid 34. When heated totemperatures of between approximately 40° C. and 80° C., the planarradiators 503 emit predominantly thermal radiation having wavelengths inthe microwave range, for which water used as the immersion liquid 34 ishighly absorptive. Alternatively, however, the heat transfer elementsmay be other components which emit electromagnetic radiation, e.g.semiconductor diodes or semiconductor lasers. Designated by 65 arethermal sensors with which the temperature of the planar radiators 503can be measured.

Associated with each planar radiator 503 is a collecting lens 66 whichfocuses the thermal radiation generated by the planar radiators 503 anddirects it at the immersion space 44. The immersion liquid 34 absorbsthe thermal radiation predominantly in the area of the boundary surface47 and is heated locally. In this way heat is generated precisely at thelocation in the immersion liquid 34 where it is lost throughevaporation. The larger the absorption coefficient for the wavelengthrange of the thermal radiation, the more strongly is the heatingconcentrated on the area of the boundary surfaces 47.

In a practical inversion of the above-described mode of operation, thearrangement shown in FIG. 6 may also be used for cooling the immersionliquid 34. In this case it is necessary only to ensure that the planarradiators 503 are cooled, e.g. by means of Peltier elements. In thiscase the heat transfer is effected by thermal radiation from warmerzones of the immersion liquid 34 to the cooled planar radiators 503.

The arrangement illustrated in FIG. 6 can be further modified so thatthe planar radiators 503 are arranged inside the projection lens 20, insuch a way that the thermal radiation emitted passes through theimmersion liquid 34 in the axial direction through suitable exitwindows. Such an arrangement may be considered particularly in the caseof measuring devices, since then there is no danger that any short-wavespectral components of the thermal radiation present will contribute toexposing the photosensitive layer 26.

FIG. 7 shows a similar portion of a projection exposure apparatusaccording to another embodiment. Unlike FIGS. 4 and 6, FIG. 7 shows awafer stage 70 on which the carrier 30 of the photosensitive layer 26 isattached. Incorporated into the wafer stage 70 are heat transferelements which, in the embodiment illustrated, are realized as conduits504 disposed parallel to one another. When a hot fluid, e.g. water,flows through the conduits 504, the zones of the carrier 30 and of thephotosensitive layer 26 located above the conduits 504 are heated. Fromthere the heat passes into the immersion liquid 34 located above saidzones. Because the conduits 504 are offset laterally with respect to theaxial position of the partial volume 48, the heat transfer is limitedsubstantially to the partial volume in the immersion space 44surrounding the partial volume 48. In this way the immersion liquid 34in the immersion space 44 is heated almost uniformly, which pre-ventsthe formation of major temperature gradients.

FIG. 8 shows in an axial section a portion of a projection exposureapparatus in which no heat transfer elements are present. In this casehomogenization of temperature distribution within the immersion liquid34 is achieved in that an evaporation barrier designated as a whole by72 is fixed to the underside 49 of the projection lens 20. Theevaporation barrier 72 comprises a total of four concentrically arrangedrings 741, 742, 743 and 744, which delimit the immersion space 44laterally, i.e. perpendicularly to the optical axis. The rings 741 to744 have, in the axial direction, a width which is such that the freeends of the rings 741 to 744 are spaced from the photosensitive layer26, as is also similarly the case with the embodiment shown in FIG. 5.In this way the photosensitive layer cannot be damaged by theevaporation barrier 72. Immersion liquid 34 located inside the immersionspace 44 is prevented by adhesion forces from escaping through the gap76 remaining between the ring 741 and the photosensitive layer 26.

Through the staggered arrangement of the rings 741 to 744 it is alsoprevented that a surrounding gas or gas mixture flows around the gap 76and thereby promotes evaporation. On the contrary, evaporated immersionliquid 34 remains predominantly in the gaps between the rings 741 to744, whereby the vapor pressure of the immersion liquid is increased inthat location. Because evaporation decreases as the vapor pressure ofthe surrounding gas increases, an evaporation-inhibiting effect isadditionally achieved in this way. This in turn has the result that onlya comparatively small temperature gradient can form inside the immersionspace 44.

FIG. 9 shows a portion of a projection exposure apparatus 10′ similar tothat shown in FIG. 1. In the case of the projection exposure apparatus10′, however, the container 32 in which the immersion liquid 34 islocated is contained by a chamber 78 sealed all round in a gas-tightmanner. The chamber 78 is formed substantially by a hood-like cover 80which has an opening 82 through which the projection lens 20 passesthrough the cover 80.

In addition, the projection exposure apparatus 10′ includes a supplyunit 84 in which elements including a reservoir 86 for immersion liquid34 and an evaporator 88 are housed. The supply unit 84 has the functionof introducing immersion liquid in the vapor phase into the chamber 78in order to increase the vapor pressure therein. For this purposeimmersion liquid withdrawn from the reservoir 86 is evaporated in theevaporator 88 and fed into the chamber 78 via a conduit 90. The vaporphase of the immersion liquid can be discharged from the chamber 78 in avalve-controlled manner via an outlet 92.

Because of the increased vapor pressure inside the chamber 78, only asmall amount of immersion liquid 34 evaporates at the boundary surface47 between the immersion liquid 34 in the liquid phase and in the vaporphase. When the saturation vapor pressure is reached in the chamber 78at the temperature prevailing therein, precisely as much immersionliquid 34 evaporates at the boundary surface 47 as is condensedinversely from the surrounding vapor phase. Therefore, as the saturationvapor pressure is reached in the chamber 78, no evaporation heat isconsumed that cools off the immersion liquid 34 located in the container32. In this way a similar effect is obtained as with the embodimentshown in FIG. 8, but without the provision of an evaporation barrier 72.The projection exposure apparatus 10′ therefore makes it possible toconduct immersion liquid 34 through the immersion space 44 in a closedcirculation.

FIG. 10 shows an enlarged portion A of the projection exposure apparatus10′ illustrated in FIG. 9. In FIG. 10 a wall 94 of the container 32 canbe seen, through which the inlet pipe 36 for the immersion liquid 34passes. For this purpose an opening 96 through which the inlet pipe 36passes into the interior of the container 32 is provided in the wall 94.The dimensions of the opening 96 are so selected that a circumferentialgap 98 that the immersion liquid 34 can penetrate remains between theinlet pipe 36 and the wall 94. On the other hand, the gap 98 is sonarrow that no immersion liquid 34 can escape from the container 32through the gap 98. In this way the inlet pipe 36, which is held bysupports 99, is mounted so as to “float” in fluid in the wall 94 of thecontainer 32. As a result, vibration of the pipe 36 which may beproduced, for example, by flow turbulence in the inlet pipe or by a pumpin the processing unit 40, cannot be transmitted to the container 32.The above-described shock-isolated mounting of inlet and outlet pipescan be of significance, in particular, for measuring devices.

FIG. 11 illustrates schematically a portion of another embodiment of aprojection exposure apparatus, denoted as a whole by 10″. In theprojection exposure apparatus 10″, to avoid shocks immersion liquid 34is not conducted into and through the container 32 by means of a pump,but only by gravity. For this purpose a reservoir 100 for immersionliquid 34 is arranged above the immersion space 44. Immersion liquid 34,controlled by a valve 104, can be conducted from the reservoir 100 intothe container 32. Periodic fluctuations in the flow velocity andvibrations caused thereby, which generally cannot be completely avoidedwith the use of pumps, do not occur with the projection exposureapparatus 102.

In this embodiment the outlet pipe 38 from the container 32 is connectedto an intercepting tank 106 in which immersion liquid 34 is collectedafter passing through a second valve 108. From there the immersionliquid is returned by means of a pump 110 to the reservoir 100 via theconditioning unit 40. Because the pump 110 is decoupled from theimmersion liquid 34 in the container 32 via the reservoir 100 and theintercepting tank 108, fluctuations in flow velocity generated by thepump 110 are confined to the pipe system between the intercepting tank106 and the reservoir 100.

Another possibility of avoiding shocks produced by pumps consists incirculating the immersion liquid 34 in the container 32 only duringprojection pauses. The containers 100 and 106 shown in FIG. 11 can thenbe dispensed with.

FIGS. 12 and 13 show a projection exposure apparatus 10′″ according to afurther embodiment in a perspective representation and in an axialsection respectively. The projection exposure apparatus 10′″ includes adetector, denoted as a whole by 120, with which undesired escaping ofimmersion liquid 34 from the immersion space 44 can be detected. Forthis purpose the detector 120 has two conductive loops 122, 124 arrangedparallel to one another in the axial direction and connected to ameasuring circuit 126.

The two conductive loops 122, 124 form a capacitor the capacitance ofwhich depends on factors including the dielectric material locatedbetween the conductive loops 122, 124. If, for example, the immersionliquid is deionized water and the surrounding gas is air, the differenceof dielectric constants is approximately 80. If immersion liquid 34 fromthe immersion space 44 enters the gap between the conductive loops 122,124, as is indicated at 128, the dielectric constant of the mediumpresent between the conductive loops 122, 124 is locally increased atthat location. The accompanying rise in the capacitance of the capacitorformed by the conductive loops 122, 124 is detected by the measuringcircuit 126. If a predefined threshold is exceeded the measuring circuit126 can, for example, generate a signal which indicates that immersionliquid has passed outside the area defined by the conductive loops 122,124.

The above embodiments have been discussed in relation to projectionexposure apparatuses. However, they are transferable, with minormodifications as appropriate, to measuring devices with which theoptical imaging characteristics of projection lenses can be determined.Such measuring devices generally include a test optics component whichis arranged, in place of the support 30 for the photosensitive layer 26,on the image side of the projection lens 20. This test optics componentmay be, for example, a mirror, a diffraction grating, a CCD sensor or aphotosensitive test layer. Such measuring devices frequently alsoinclude separate light sources which then replace the illuminationsystem of the projection exposure apparatus.

Some of the above-described embodiments and aspects of the invention canbe used especially advantageously with certain measuring devices. Withregard to a Shearing interferometer this is the case, for example, forthe variants shown in FIGS. 3 to 5 and the floating mounting of pipesshown in FIG. 10; the circulation making use of gravitation illustratedin FIG. 11 is especially advantageous with a Moiré interferometer.

FIG. 14 illustrates schematically a pinhole mask of a point diffractioninterferometer (PDI) in an axial section. Such point diffractioninterferometers and the pinhole masks necessitated thereby are known perse in the prior art, so that elucidation of further details thereof canbe omitted. The pinhole mask 140 consists of a glass body 142 to which asemitransparent layer 144 is applied. Located at approximately thecentre of the pinhole mask 140 is a small pinhole opening 146 in thesemitransparent layer 144.

To be able to heat the immersion liquid 34 in the immersion space 44located above said semitransparent layer 144 in the partial volumesurrounding the partial volume 48 exposed to the measuring light,conduits 148 through which flows a fluid heating medium, e.g. heatedwater, are incorporated in the glass body 142. In this way the peripheryof the glass carrier 142 is heated uniformly, whereby the temperature ofthe immersion liquid 34 located above same is increased locally.

FIG. 15 shows another embodiment of a pinhole mask, denoted by 140′, ina representation corresponding to FIG. 14. In this embodiment thepinhole mask 140 consists of a metal carrier 142′ at the centre of whicha glass insert 150 is incorporated. This glass insert 150, which mayhave the form, for example, of a truncated cone, is so dimensioned thatthe measuring light can pass through the glass insert 150 withoutreaching the surrounding metal of the metal carrier 142′.

Because the volume 48 through which the measuring light passespredominantly borders the metal carrier 142′ via the semitransparentlayer 144 and only a small part thereof borders the glass insert 150,heat released in the volume 48 by absorption of measuring light isefficiently dissipated via the metal carrier 142′. In this way the highthermal conductivity of the metal carrier 142′ contributes to permittingonly a small temperature gradient within the immersion space 44.

FIG. 16 shows in a partial perspective representation a projectionexposure apparatus according to still another embodiment. In thisembodiment immersion liquid (not shown) is applied to the immersionspace 44 formed between the terminal plate 54 of the projections lens 20and the photosensitive layer 26 with the help of a plurality of inlets202 a, 202 b, 202 c. The inlets 202 a, 202 b, 202 c are connected to adistributor 204 which is supplied with immersion liquid via a supplyline 206.

On the opposite side of the inlets 202 a, 202 b, 202 c a plurality ofoutlets 208 a, 208 b, 208 c is arranged such that they reach into theimmersion space 44. The outlets 208 a, 208 b, 208 c are connected to animmersion liquid collector 210 through which immersion liquid sucked invia the outlets 208 a, 208 b, 208 c and collected in the collector 210is drained away through a drain line 212.

During operation of the projection exposure apparatus immersion liquid34 is constantly or intermittently supplied via the inlets 202 a, 202 b,202 c and sucked off with the help of the outlets 208 a, 208 b, 208 c.Thus there is a constant or frequent exchange of immersion liquidfilling the immersion space 44.

The projection exposure apparatus further comprises a temperature sensor214 which is arranged such that it reaches into the immersion space 44.The temperature sensor 214 and the distributor 204 for the inlets 202 a,202 b, 202 c are connected to a control unit 216. An additional cap maybe provided that substantially seals off the immersion space 44 from theouter atmosphere, as is known in the art. Such caps are sometimesreferred to as “shower hood”.

FIG. 17 shows a radial cross section through the inlet 202 a. The crosssections of the other inlets 202 b, 202 c are, in the embodiment shown,identical. The inlet 202 a comprises an inlet wall 216 which is formedby a flexible hose or a rigid tube, for example. Within the inlet wall216 a plurality of elongated heating elements 218 extend along thelongitudinal direction of the inlet 202 a. The heating element 218 maybe formed by heating wires or channels through which heated or cooledwater or another heat carrier fluid is guided. By appropriatelycontrolling the heating elements 218, it is possible to change thetemperature of the immersion liquid leaving the inlet 202 a and runninginto the immersion space 44.

In a preferred embodiment each inlet 202 a, 202 b, 202 c can becontrolled independently at least as far as the heating elements 218 areconcerned. Alternatively or additionally, the flux (i.e. flow rate) ofimmersion liquid running through the inlet 202 a, 202 b, 202 c may beindependently set in the distributor 204 under the control of thecontrol unit 216.

It is thus possible to locally change the temperature of the immersionliquid within the immersion space 44 by selectively controlling theheating elements 218 and/or the flow rate for each inlet 202 a, 202 b,202 c. From this it becomes clear that the spatial resolution of thistemperature control of the immersion space 44 depends on the number andarrangement of inlets 202 a, 202 b, 202 c provided around the immersionspace 44. By appropriately selecting these parameters it is possible toachieve a homogenous temperature distribution at a target temperature,or at least a rotationally symmetric temperature distribution having atarget temperature gradient, within the partial volume of the immersionspace 44 that is exposed to projection light.

As a matter or course, there are various alternatives for the inlets 202a, 202 b, 202 c as far as the temperature control is concerned. Forexample, the heating elements 218 may extend through the inlet wall 216like a helix, or they may be configured as a mesh woven of a conductingwire.

In the embodiment shown the temperature sensor 214 is part of a controlloop that makes it possible to keep the temperature within the immersionspace 44, or at least the temperature in the vicinity of the temperaturesensor 214, at a constant value. Preferably the maximum variations ofthe temperature of the immersion liquid 34 should not exceed 5 mK, andeven better 2 mK, during a duration of 1 minute. Over longer timeperiods, for example 15 minutes, these limits may be considerablyrelaxed up to a factor 10. These values ensure that the temperaturevaries slowly enough to be able to correct residual imaging aberrationsby means further explained below.

Certain parameters that detrimentally affect the temperature stabilitymay be quantitatively determined beforehand, either by simulation or byexperiment. For example, a simulation model may be developed that makesit possible to predict the amount of immersion liquid that evaporatesduring the operation of the apparatus, and how this evaporation affectsthe temperature of the immersion liquid within the partial volume of theimmersion space 44 that is exposed to projection light. With the help ofthe controllable inlets 202 a, 202 b, 202 c this expected temperaturevariation may be compensated for. Thus the temperature may be maintainedat a constant or only slowly varying value even if no closed controlloop comprising the temperature sensor 214 is provided.

In FIG. 16 the temperature sensor 214 is illustrated as a single elementthat reaches into the immersion space 44. However, the temperaturemeasurement of a complex 3D temperature distribution is a difficulttask, and often it is not easy to accurately determine the 3Dtemperature distribution on the basis of measurements performed only ata small number of measurement points.

Another alternative for measuring the temperature of the immersionliquid 34 is shown in the cross section of FIG. 18. In this embodiment amatrix of temperature sensors 214′ is received within a wafer stage 70for positioning the carrier 30 relative to the projection lens 20. Sincethe carrier 30 is usually made of a material having a large heatconductivity, the temperature distribution of the immersion liquid 34over the area of the matrix of temperature sensors 214′ may be measuredby the temperature sensors 214′ with high accuracy.

Temperature sensors may also be provided at or in the outlets 208 a, 208b, 208 c.

The temperature of the immersion liquid may also be determined moreremotely from the immersion space 44 on the basis of opticalmeasurements. For example, the refractive index of the immersion liquid,and thus its temperature, may be determined by interferometricmeasurements that measure phase deviations of measurement lightpropagating through the immersion liquid 34 substantially parallel tothe photosensitive layer 26. Another possibility is to measure infraredradiation emitted by the immersion liquid. If a cap (“shower hood”) isprovided, this cap may contain a window which is transparent for thisinfrared radiation.

Instead of or in addition to the control of the outlets 202 a, 202 b,202 c on the basis of measured temperature data, certain imagingproperties of the projection lens 20 may be measured and directly fed tothe control unit 216. For example, alignment marks arranged on thecarrier 30 are usually optically detected. If the alignment marks arecompletely immersed in immersion liquid, the temperature and thus therefractive index of the immersion liquid will also have an impact on theoptical detection of the alignment marks.

The information obtained from the optical detection equipment may beused to control the temperature of the immersion liquid.

The above mentioned methods and devices to measure the temperature ofthe immersion liquid may be used also in conjunction with embodiments inwhich no means for selectively varying the temperature in a partialvolume of the immersion space are provided, as is the case in theembodiments described above. A global change of the temperature of theimmersion liquid may be achieved, for example, by mixing two immersionliquids having different temperatures with a carefully selected mixingratio, or by inductive heating of a single inlet.

If no means are provided to achieve a homogenous or at leastrotationally symmetric temperature distribution, or if significantresidual imaging aberrations remain in spite of the application of suchmeans, it may be necessary to apply methods for correcting the residualimaging aberrations. To this end many of the known manipulators forcorrecting imaging aberrations may be advantageously used. For example,the last lens element and/or other lens elements of the projection lens20 may be displaced along or tilted with respect to the optical axis, orsuch lens elements may be deformed. If the temperature distribution ofthe immersion liquid is rotationally symmetric, the deformations of thelens element(s) should be rotationally symmetric as well.

Other manipulators may vary the gas pressure in a confined volumethrough which projection light propagates.

It is also possible to design the projection lens 20 such thattemperature variations occurring in the last lens element result in acompensation of the effects caused by a temperature change in theimmersion liquid. This principle exploits the fact that the last lenselement is thermally coupled to the immersion liquid, and thus aself-correcting effect may be produced by appropriately designing theproperties of the last lens elements.

Manipulators may be preferably used in those cases in which short termtemperature fluctuations of the immersion liquid have to be compensatedfor. This is due to the fact that a temperature fluctuation of theimmersion liquid immediately results in optical aberrations that requireinstant correction, whereas it usually takes some time to change thetemperature of the immersion liquid using one of the methods and devicesdescribed above. In a preferred embodiment a fine correction of residualimaging aberrations is therefore carried out even during the exposureoperation. Larger aberrations are corrected in exposure pauses bychanging the temperature of the immersion liquid.

The above description of the preferred embodiments has been given by wayof example. From the disclosure given, those skilled in the art will notonly understand the present invention and its attendant advantages, butwill also find apparent various changes and modifications to thestructures and methods disclosed. The applicant seeks, therefore, tocover all such changes and modifications as fall within the spirit andscope of the invention, as defined by the appended claims, andequivalents thereof.

1.-47. (canceled)
 48. An exposure apparatus which exposes a substrate byradiating an exposure light beam onto the substrate through a liquid,the exposure apparatus comprising: a substrate stage which has asubstrate-holding member for holding the substrate and which is movablewhile holding the substrate by the aid of the substrate-holding member;and a temperature adjustment system which performs temperatureadjustment for the substrate-holding member.
 49. The exposure apparatusaccording to claim 48, wherein the temperature adjustment systemperforms the temperature adjustment for the substrate-holding member sothat heat transfer is reduced between the substrate and the liquid onthe substrate.
 50. The exposure apparatus according to claim 48, whereinthe temperature adjustment system performs the temperature adjustmentfor the substrate-holding member so that no temperature change of theliquid is caused by contact between the liquid and the substrate. 51.The exposure apparatus according to claim 50, wherein the temperatureadjustment system performs the temperature adjustment for thesubstrate-holding member so that no temperature distribution isgenerated in the liquid.
 52. The exposure apparatus according to claim48, wherein the temperature adjustment system performs the temperatureadjustment for the substrate-holding member so that no temperaturechange of the substrate is caused by contact between the liquid and thesubstrate.
 53. The exposure apparatus according to claim 48, wherein thetemperature adjustment system uses a liquid which is same as the liquidto be supplied onto the substrate to perform the temperature adjustmentfor the substrate-holding member.
 54. The exposure apparatus accordingto claim 48, wherein the temperature adjustment system performs thetemperature adjustment for the substrate-holding member depending on atemperature of the liquid to be supplied onto the substrate.
 55. Theexposure apparatus according to claim 48, further comprising atemperature sensor which measures a temperature of the substrate-holdingmember.
 56. The exposure apparatus according to claim 48, wherein thetemperature adjustment system also performs temperature adjustment foran optical member through which the exposure light beam passes, in astate in which the optical member makes contact with the liquid.
 57. Theexposure apparatus according to claim 48, wherein the temperatureadjustment system also performs temperature adjustment for the liquid.58. An exposure apparatus which exposes a substrate by radiating anexposure light beam onto the substrate through a liquid, the exposureapparatus comprising: a temperature adjustment system which performstemperature adjustment for an optical member through which the exposurelight beam passes in a state in which the optical member makes contactwith the liquid.
 59. The exposure apparatus according to claim 58,wherein the temperature adjustment system performs the temperatureadjustment for the optical member so that heat transfer is reducedbetween the liquid and the optical member.
 60. The exposure apparatusaccording to claim 58, wherein the temperature adjustment systemperforms the temperature adjustment for the optical member so that notemperature change of the liquid is caused by contact between the liquidand the optical member.
 61. The exposure apparatus according to claim60, wherein the temperature adjustment system performs the temperatureadjustment for the optical member so that no temperature distribution isgenerated in the liquid.
 62. The exposure apparatus according to claim48, further comprising: a projection optical system which projects animage of a pattern onto the substrate through the liquid; and atemperature sensor which measures a temperature of the liquid suppliedto an image plane side of the projection optical system.
 63. Theexposure apparatus according to claim 58, wherein the temperatureadjustment system performs the temperature adjustment for the opticalmember so that no temperature change of the optical member is caused bycontact between the liquid and the optical member.
 64. The exposureapparatus according to claim 58, wherein the temperature adjustmentsystem performs the temperature adjustment for the optical memberdepending on a temperature of the liquid to be supplied onto thesubstrate.
 65. An exposure apparatus which exposes a substrate byradiating an exposure light beam onto the substrate through a liquid,the exposure apparatus comprising: a substrate stage which is movablewhile holding the substrate and which has a member forming a flatportion around the substrate; and a temperature adjustment system whichperforms temperature adjustment for the member forming the flat portion.66. The exposure apparatus according to claim 65, wherein thetemperature adjustment system performs the temperature adjustment sothat no temperature change of the member forming the flat portion iscaused.
 67. The exposure apparatus according to claim 65, wherein thetemperature adjustment system performs the temperature adjustment forthe member forming the flat portion to suppress temperature change ofthe liquid on the flat portion.
 68. The exposure apparatus according toclaim 48, further comprising a projection optical system which projectsan image of a pattern onto the substrate through the liquid.
 69. Anexposure apparatus which exposes a substrate by radiating an exposurelight beam onto the substrate through a liquid, the exposure apparatuscomprising: a liquid supply mechanism which supplies the liquid; and atemperature sensor which measures a temperature of an object that makescontact with the liquid supplied from the liquid supply mechanism,wherein: the liquid supply mechanism adjusts a temperature of the liquidto be supplied on the basis of a measurement result obtained by thetemperature sensor.
 70. The exposure apparatus according to claim 69,further comprising: a projection optical system which projects an imageof a pattern onto the substrate through the liquid supplied from theliquid supply mechanism, wherein: the liquid supply mechanism suppliesthe liquid to an image plane side of the projection optical system; thetemperature sensor measures the temperature of the object which makescontact with the liquid supplied from the liquid supply mechanism to theimage plane side of the projection optical system; and the liquid supplymechanism adjusts the temperature of the liquid to be supplied the imageplane side of the projection optical system on the basis of themeasurement result obtained by the temperature sensor.
 71. The exposureapparatus according to claim 69, wherein the object includes thesubstrate.
 72. The exposure apparatus according to claim 69, furthercomprising: a projection optical system which projects an image of apattern onto the substrate through the liquid supplied from the liquidsupply mechanism, wherein: the object includes a part of optical membersof the projection optical system.
 73. The exposure apparatus accordingto claim 69, further comprising: a substrate stage which is movablewhile holding the substrate, wherein: the object includes a member whichforms at least a part of an upper surface of the substrate stage. 74.The exposure apparatus according to claim 73, wherein the member, whichforms at least the part of the upper surface of the substrate stage,includes a measuring member which is provided in the substrate stage.75. The exposure apparatus according to claim 69, wherein thetemperatureadjusting unit adjusts the temperature of the liquid to besupplied so that the temperature of the liquid to be supplied issubstantially same as the temperature of the object.
 76. A method forproducing a device, comprising using the exposure apparatus as definedin claim
 48. 77. An exposure method for exposing a substrate through aliquid, the exposure method comprising: adjusting a temperature of thesubstrate in consideration of a temperature of the liquid beforestarting exposure for the substrate; and exposing the substrate byradiating an exposure light beam onto the substrate through the liquid.78. The exposure method according to claim 77, wherein the exposurelight beam is radiated onto the substrate via a projection opticalsystem and the liquid to expose the substrate.
 79. The exposure methodaccording to claim 77, wherein the temperature of the substrate isadjusted before loading the substrate on a substrate stage which ismovable while holding the substrate during the exposure for thesubstrate.
 80. The exposure method according to claim 77, wherein thetemperature of the substrate is adjusted after loading the substrate ona substrate stage which is movable while holding the substrate duringthe exposure for the substrate.
 81. The exposure method according toclaim 80, wherein the liquid, which is to be used for the exposure forthe substrate, is supplied onto the substrate loaded on the substratestage to adjust the temperature of the substrate.
 82. The exposuremethod according to claim 77, wherein the liquid, which is to be usedfor the exposure for the substrate, is used to adjust the temperature ofthe substrate.
 83. The exposure method according to claim 79, whereinthe temperature of the substrate is adjusted before loading thesubstrate on the substrate stage so that the temperature change in theliquid is small when the substrate and the liquid make contact with eachother.
 84. The exposure method according to claim 83, wherein thetemperature of the substrate is adjusted before loading the substrate onthe substrate stage so that the temperature change in the substrate issmall when the substrate is loaded on the substrate stage.
 85. A methodfor producing a device, comprising using the exposure method as definedin claim
 77. 86. An exposure method for exposing a substrate through aliquid, the exposure method comprising: adjusting a temperature of anobject which includes the substrate and makes contact with the liquid,on the basis of a predetermined temperature; and exposing the substratethrough the liquid which has the predetermined temperature.
 87. Theexposure method according to claim 86, further comprising measuring thetemperature of the object.
 88. The exposure method according to claim87, wherein the temperature of the object is adjusted on the basis ofthe predetermined temperature and the measured temperature of theobject.
 89. The exposure method according to claim 86, wherein thesubstrate is exposed through the liquid having the predeterminedtemperature while adjusting the temperature of the object which makescontact with the liquid on the basis of the predetermined temperature.90. An exposure method for exposing a substrate by radiating an exposurelight beam onto the substrate through a liquid, the exposure methodcomprising: supplying the liquid; and adjusting a temperature of theliquid to be supplied, on the basis of a temperature of an object whichmakes contact with the supplied liquid.
 91. The exposure methodaccording to claim 90, wherein: the exposure light beam is radiated ontothe substrate via a projection optical system; and the object is a partof the substrate or an optical member of the projection optical system.92. The exposure method according to claim 90, further comprisingholding the substrate on a substrate stage, wherein the object is amember which is provided on an upper surface of the substrate stage. 93.The exposure apparatus according to claim 58, further comprising: aprojection optical system which projects an image of a pattern onto thesubstrate through the liquid; and a temperature sensor which measures atemperature of the liquid supplied to an image plane side of theprojection optical system.
 94. The exposure apparatus according to claim58, further comprising a projection optical system which projects animage of a pattern onto the substrate through the liquid.
 95. Theexposure apparatus according to claim 65, further comprising aprojection optical system which projects an image of a pattern onto thesubstrate through the liquid.
 96. A method for producing a device,comprising using the exposure apparatus as defined in claim
 58. 97. Amethod for producing a device, comprising using the exposure apparatusas defined in claim
 65. 98. A method for producing a device, comprisingusing the exposure apparatus as defined in claim 69.